Nitrogen fixation is carried out by:

1.	bacteria	2.	fungi
3.	protists	4.	algae

What percent of the energy fixed by primary producers in a typical field ecosystem is received by a secondary consumer?

The rate at which energy is converted by photosynthetic and chemosynthetic autotrophs to organic substances is called as:
1. biomass
2. transpiration
3. net primary productivity
4. gross primary productivity

The chemical energy that is not converted to new biomass in the process of energy transfer between trophic levels in an ecosystem is finally:
1. removed in the feces
2. recycled by decomposers
3. used by heterotrophs to thermoregulate.
4. dissipated into space as heat

The percent of the sun’s energy captured by plants is approximately:

Aquatic ecosystems that are most adversely affected by acid are those that lack:
1. calcium
2. carbonic acid
3. nitrate
4. bicarbonate

The largest net primary production of the Earth is contributed by:
1. savanna
2. salt marsh
3. open ocean
4. tropical rainforest

An example of primary succession would be:

The residual, after autotrophic respiration is subtracted from GPP, is:

Energy and nutrients enter an ecosystem and hence in a community through:
1. Producers
2. Consumers
3. Detritivores
4. Apex predators